Seatbelt Entanglement: Field Analysis, Countermeasure Development, and Subject Evaluation of Devices Intended to Reduce Risk

Since 2000, over 200 rear seat occupants have become entangled in the seatbelt when they inadvertently switched it from emergency locking mode (ELR) to automatic locking mode (ALR). Since a method is needed to lock the seatbelt when installing child restraint systems (CRS), the National Highway Traffic Safety Administration (NHTSA) commissioned tool, inc. to develop prototype devices that could reduce the risk of seatbelt entanglement resulting from the lockability requirement. A field analysis of entanglement incidents was first conducted to inform countermeasure design. Prototype devices were developed and evaluated through testing with volunteer subjects in comparison to standard seatbelt systems by assessing how different designs would be used to install CRS, the quality of the resulting installations, how users would disentangle a trapped child surrogate, as well as to identify volunteer experience when using the belts themselves. Four prototype devices were evaluated in two phases of testing conducted at the UMTRI. All four prototype devices had shorter disentanglement times than trials with the standard seatbelt, but there was not a statistically significant difference between the devices. There were no substantial differences in the quality of child restraint installation among the devices and the standard seatbelt.